Self-lowering screw jack



June 15 1926.

F. H. SCHWERIN SELF LOWERING SCREW JACK Filed May 15, 1924 s Sheets-Shet 1 ATTORNEY June 15 1926. 1,589,000

F. H. SCHWERIN SELF LOWERING SCREW JACK Filed May 15, 1924 3 Sheets-Sheet 2 A TTORNEY F. H. SCHWERIN SELF LOWERING SCREW JACK June 15 1926.

Filed May 15. 1924 3 Sheets-Sheet 5 A TTOR/V E Y Patented June 15, 1926.

UNITED STATES 1,589,000 PATENT OFFICE.

FRANK H. SCHWERIN, OF BELLEVUE, PENNSYLVANIA, ASSIGNGR TO THE DUFF MANUFACTURING COMPANY, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

SELF-LOWERING SCREW JACK.

Application filed l\'lay 15, 1924. Serial No. 713,427.

The invention relates to that kind of selflowering high-speed screw-jack covered by the Hindman Patent 1,23%334: of July 24, 1917, having automatic and manual brake mechanism by means of which both the speed and the extent of the lowering may be per fectly controlled without jarring or injury to the jack, its load, or its support, under maximum loads. The present invention employs the means of the said patent for effecting safe and speedy lowering and stopping of a heavily loaded jack, the object being to embody the same in a perfected form, in a ack of generally improved style,

1 containing general features of the Kopf and Schwerin Patent 1,329,665, dated February 3, 1920.

In the accompanying drawings forming part hereof: V

Fig. 1 is an elevation of a jack of the present invention;

Fig. 2 is a sectional elevation, the section being taken on an irregular line indicated approximately by the line 2 2 of Fig. 3; and

Fig. 3 is a fragmentary sectional elevation taken on an irregular line indicated approximately at 33 in Fig. 1.

The jack has a wide base 2, having ahollow standard 3 rising therefrom, and a relatively low annex 4 the chamber of which is open to the interior of the base and standard. The portions 2, 3, 4 constitute an enclosed base-frame or base.

A bearing 5 in the upper end of the stationary standard laterally supports and guides an internal ram or load member 6, presenting a small head 7. The ram is kept from turning by a key 8 in the standard engaging a groove in the ram, as in the said Kopf and Schwerin patent.

The ram is hollow, and its lower end contains a nut or female screw member"). A male screw 10 rotatably supported on the base by a ball bearing 11 extends upward in threaded engagement through the nut and into the hollow interior of the ram. The screw elements are of steep pitch so that the ram will run down under the load.

The operating means for lifting the load member and its load includes a horizontal lifting shaft 12 journaled in a bearing in a wall of the lower part of the annex, the inner end of this shaft having fixed thereon a bevel pinion 13 which meshes with a large bevel gear wheel 14: on the lower extension of the screw 10. The shaft 12 is operated step by step in the usual manner by a pawlcarrying lever socket 15 mounted to'os'cillate on the outer portion of the rotatable shaft, and cooperating with a ratchet-wheel 16 fixed on the shaft. 7

At the end of each lifting stroke, the load would drop back, to prevent which and to provide for'sure lowering and stopping the auxiliary train and mechanism are provided. The primary element of this train is a large spur-gear wheel 17 fast on the operating shaft 12, so as to rot-ate in both directions therewith. All the remainder of the holding and lowering and stopping mechanism, including the one-way-acting automatic clutch which causes the lifting to be free of the holding means and multiplying train, is carried by a removable vertical plate 18, which is fastened by screws 18* over an opening in a wall of the annex 4 above and parallel with the operating shaft 12. V

The said plate has spaced wing walls 19 and 20 projecting therefrom at right angles inwardly of the annex chamber, and joined at the top and rear by a bearing 21. Shafts 22 and 23, one above the other and both above the shaft 12, are supported by and between the said wing walls, parallel with the cover plate 18 and with the said operating shaft. A shaft 24 is journaled in the bearing 21 and in a bearing 25 secured by a screw 26 in an opening in an internal boss 27 of the plate 18, this shaft being at right angles to the other shafts and perpendicular to the plate. I

On the shaft 23, in position to mesh with the upper part of the gear 17, below its top toward the side nearer the plate 18, is a pinion or small spur-gear wheel 28, and united with this pinion, as by means of a sleeve 29, is a ratchet-Wheel 30, forming one member of a one-Way clutch.

A large spur-gear wheel 31 is mounted loosely on the axis 23, between the pinion 28 and the ratchet-wheel 30, and has pinned to it a hollow pawl-carrier disk 32, which has bearing on the shaft between the gear wheel 31 and the wing-wall 20. The spring- ,pressed pawls 33 of this carrier cooperate.

in a known manner with the ratchet-wheel 29, so that on the lifting strokes, the pawls click idly over the inclined sides of the teeth, the gear wheels 17 and 28 and the pawl-carrier 32 being rotated by the operating shaft, while the remainder of the auxiliar mechanism is stationary. At the end of each lifting stroke, the load is prevented from descending by reason of the pawls engaging in a holding manner with the abrupt sides of the teeth of the ratchet wheel, which in turn is held through the reducing gearing by the brake.

The spur-gear wheel 31, which is not turned on the lifting strokes, meshes with a small gear-wheel 34 on the axis 22. This wheel is coupled with a worm-wheel 35, which meshes a worm 36 on the shaft 24. The worm-wheel and worm are of steep pitch, so that the worm-wheel will drive the worm, forming the terminal unit of the speed-multiplying train.

A pocket chamber 3'? in the upper part of the cover plate, at the outer side of the internal boss 27, and closed by a .small removable bossed cover 38 secured to the main plate by screws 39, contains the brakes.

A head 40 pinned to the worm shaft with in this chamber carries a pair ofcentrifugal weights 41. The said weights have oll'set stems 42, which are pivoted on pins 43 in slots of the head, and the bodies of the weights are of curved segmental form so as to coact frictionally with the adjacent encircling interior wall 44 of the external brake chamber.

The inner forward portions of the centrifugal members 41 are beveled for cooperation with a conical wedge member 45, which is coaxial with the shaft 24 and capable of adjustment in opposite longitudinal directions by means of a screw 46 of low, selfholding pitch threaded through the outer side of the cover 38. The inner journal end 47 of the screw is swiveled in the wedge and headed and shouldered as shown so as to both advance and retract the wedge positively. A finger-piece 48 on the outer end of the screw provides convenient manual operation. The wedge is shown provided with a central bore 49 affording a bearing on the end of the worm shaft 24, in addition to which a pin 50 may be provided, guided in a hole in the cover.

The manual brake is normally set through the parts 48, 46, 45, so as to lock the centrifugal segments 41 of the automatic speed-controlled brake against the wall 44. Thereby the load will be held at any height to which it may be lifted by the main operating means and the main lifting screw 10. To lower the load, the manually controlled brake is released by slightly retracting the wedge 45 by its screw. This frees the seg ments 41, so that the jack runs down, thereby driving the speed-multiplying auxiliary train. The centrifugal action at the highspeed shaft 24 acts to urge the revolving weights 41 outward against the wall 44, and does so with increasing force before dangerous speeds are attained, thereby automatically checking the descent, and causing the loaded jack to set its own rate of lowering, the greater load producing the greater retarding force. The speed thus regulated permits the hand-lock to be quickly and positively applied to stop the load at an exact point without jar or tearing of gears or injury to the brake mechanism. The location of the one-way clutch 29, 30, on the lower shaft 23 of the cover plate, which is the second shaft of the auxiliary train, enables this mechanism to be readily removed, and permits of greater compactness than if it were placed on the main operating shaft, because of the smaller size of the clutch parts required to hold the load at this point. At the same time the number of parts of the train that must be rotated with each lifting ctiort, namely the wheels 17 and 2t and the pawl-carrier 32, do not constitute an appreciable resistance.

The manner in which the manual and automatic brakes are combined for cooperation is especially effective for the purpose of these jacks.

It is to be understood that I do not necessarily limit myself to the precise form described, since there may be various omissions, additions, or changes in detail.

\Vhat I claim as new is:

1. A self-lowering lifting-jack having a steep-pitch lifting screw, operating means, an auxiliary train of gearing having a oneway-acting clutch, a brake shaft to be driven by said train only in the load-lowering direction, an automatic speed-controlled braking device operated by said shaft and auxiliary gearing, and a manually controlled braking device adapted to operate upon said speed-controlled braking device.

2. A self-lowering lifting-jack having a. steep-pitch lifting screw, operating means to effect lifting, an auxiliary gearing, an automatic governor brake comprising centrifugal elements to be driven by said auxiliary gearing, and normally controlled means for locking against said governor elements. 7

3. A self-lowering lifting-jack having a steep-pitch lifting screw, operating means to effect lifting, an auxiliary gearing, an automatic governor brake comprising cen trifugal weight members to be driven by said auxiliary gearing, and positive manual means adapted to lock against said centrifugal members.

4. A self-lowering lifting-jack having a steep-pitch lifting screw, operating means to effect lifting, an auxiliary gearing, an automatic governor brake comprising centrifugal weight members to be driven by said auxiliary gearing, a frictional lock for said governor brake applicable directly to said centrifugal members, and manual means adapted to both positively apply and release said lock.

5. A self-lowering lifting-jack having a steep-pitch lifting screw, operating means, an auxiliary gearing having a one-way-acting clutch, a brake shaft to be driven by said gearing only in the load-lowering direction, an automatic speed-controlled braking device operated by said shaft and auxiliary gearing, said automatic device comprising centrifugal members driven by the shaft so as to be urged against an encircling stationary wall, and a manually controlled wedge clevice operative between said centrifugal members to press the centrifugal members against the encircling wall.

6, A self-lowering lifting-jack having a steep-pitch lifting screw, operating means, an auxiliary gearing having a one -way-acting clutch, a brake shaft to be driven by said gearing only in the load-lowering direction, an automatic speed-controlled braking device operated by said shaft and auxiliary gearing, said automatic device comprising centrifugal members driven by the shaft so as to be urged against an encircling stationary wall, a conical Wedge operative between said centrifugal members to lock them against said wall, and a manually-operated screw for operating the Wedge. c

7. A self-lowering lifting-jack comprising a base having a standard rising therefrom and an annex, a lifting ram guided in the top of the standard, a steep-pitch screw rotatably mounted on the base and extending upward within the ram, a horizontal operating shaftin the base annex geared to the screw, a spur gear wheel on said shaft forming the first or driving element of an auxiliary multiplying train of gears, a driven gear wheel in the annex above and meshing with said driving gear wheel, a loose gear wheel coaxial with said driven gear wheel, and an intermediate one-way-ac'ting clutch on the same axis, together with further elements of said auxiliary train above and driven through said loose gear wheel only in the load-lowering direction and terminating in a worm gear, and automatic and manual brake devices cooperating with the worm gear.

FRANK H. SCHWERIN. 

